Currently operating in the United States is a class of small race cars which incorporates motorcycle engines for propulsion and chain drive systems for power transmission. This basic power transmission set-up has two major drawbacks: First, the geometry of the chassis suspension causes vertical movement of the driven axle. This results in the drive chain being subjected to continual slackening and tightening cycles as the vehicle travels over the road or track. This causes the chain to suffer fatigue and stretch which can result in failure of the chain or make the chain very susceptible to derailing. Second, if the first condition is corrected by modifying the suspension geometry of the chassis to follow a nonslackening arc then the movement of the wheel base, the distance between the front axle and the rear axle, is adversely affected to cause lengthening and shortening of the wheel base as the car travels. This adversely affects the handling of the vehicle.
As noted previously a slack chain is very susceptible to derailing. This is especially true at the high rotational speeds involved in auto racing. Previously the problem of derailing was addressed by use of a spring loaded idler sprocket. This allowed proper chain tension to be maintained with the desired vertical suspension geometry. This works but it absorbs horsepower, a serious drawback in a racing vehicle, and still the spring idler may be overwhelmed at high speeds with resulting chain derailments. Also, all the driving force or chain tension must be reacted to by the suspension system. This can lead to a binding condition which is very detrimental to the handling of a race car.
Further, an additional problem with the current drive systems is that the chassis and the drive sprocket have a tendency to roll and move vertically with respect to the driven axle. This causes the two sprockets to be out of plane, adds to chain bind, and is an additional cause of chain derailing.
Finally, the presently used geometry of small chain driven racing cars is such that it is impossible to run a chain at the center of the car because a straight line path there would take the chain where the driver's seat must be. Accordingly, the chain has had to be to one side of the driver. That in turn means that the spring loaded mount for the chain tightening idler sprocket causes the sprocket to tilt on its edge as it moves up and down in an arc. This can, by itself, cause chain mis-alignment which causes the chain to jump off one or more of the sprockets. In addition, as was previously noted, there is a drag from the chain tightening sprocket, which is increased by mis-alignment between that sprocket and the path of the chain which affects the transmission of power from the engine to the wheels.
It is the objective of my present invention to overcome this problems by means of my unique and simple design which is disclosed herein. I know of no other structure or design which either teaches or shows the device of my invention. For example, U.S. Pat. No. 649,689 (Gay) shows a rear wheel that can move vertically on a leaf spring and it shows a sprocket system having two chains and an intermediate idler sprocket. The idler sprocket is spaced from the axle by a link Q' and it is spaced from the chassis by a link M' (which appears to be incorrectly located). These are different from my present invention in that the placement of strut or link M' will not function to keep the drive chain J at the proper tension. Furthermore, strut M' is connected to the hub of the intermediate sprocket rather than being connected in the manner and location of my present invention so that the geometry of my invention is different and more effective. U.S. Pat. No. 2,800,188 merely shows a system of multiple chains and sprockets without my structure. U.S. Pat. No. 2,927,480 shows a multiple drive with a link 57 controlling the position of the intermediate shaft but it does not teach my present invention and lacks the tensioning strut of the present invention. U.S. Pat. No. 2,479,617 likewise shows a dual chain drive with an intermediate sprocket but the entire assemblage is inside a rigid housing. A fixed adjustment for chain tension is shown. U.S. Pat. No. 4,328,877 is somewhat relevant in that the arrangement of this multiple chain drive does permit the wheel to move without slackening the chain but a very different suspension is shown. U.S. Pat. No. 1,168,934 discloses a multiple chain drive but the axle is fixed.
It is the objective of the present invention to provide a geometry which allows vertical movement of the driven axle while preventing the drive chain from being subjected to continual slackening and tightening cycles as the vehicle travels over the road or track.
It is a further objective of the present invention to allow the vehicle to move freely around any designed in shortcomings of the vehicle in which it is installed without chain bind.
It is a further objective of the present invention to prevent slackening and derailment of the chain with absorbing little or no horsepower or causing a binding of the chain.
Finally, it is an objective of the present invention to allow the chassis and the drive sprocket to roll and move vertically with respect to the driven axle by minimizing the angularity change of a normal big sprocket to small sprocket final drive system. This plane may now be on the centerline, under the driver, because my new geometry permits it or anywhere in the vehicle that it is desired.